Dosimetry Apparatus, Systems, and Methods

ABSTRACT

A direct ion storage (DIS) radiation detector or dosimeter has a design that is easy and low cost to manufacture using semiconductor processing techniques. The detectors include internal communications interfaces so they are easy to read. Different interfaces, including wired, e.g. USB ports, and wireless interfaces, may be used, so that the dosimeters may be read over the internet. The detectors can thus be deployed or used in a variety of detection systems and screening methods, including periodic or single time screening of people, objects, or containers at a location by means of affixed dosimeters; screening of objects, containers or people at a series of locations by means of affixed dosimeters, and surveillance of an area by monitoring moving dosimeters affixed to people or vehicles.

BACKGROUND

1. Field

This invention pertains generally to radiation detection, and moreparticularly to direct ion storage (DIS) dosimeters, and mostparticularly to their fabrication and data retrieval. The invention alsopertains to radiation detection systems and methods based on multipledosimeters, including multiple DIS dosimeters.

2. Description of Related Art

There are many different types of radiation detectors or dosimeters formonitoring exposure to hazardous ionizing radiation, such as x-rays,gamma rays, electrons and neutrons. These range from simple colorimetricfilm or badge dosimeters to complex electronic devices. Some devices arereal-time; others show a cumulative exposure over a long period of time.A wide range of dosages may be detected.

One particular type is the direct ion storage (DIS) dosimeter, as shownin U.S. Pat. No. 5,739,541. A DIS dosimeter is based on a MOSFET with afloating gate on which a charge is placed. The surface of the gate isopen to a space containing air or other gas, usually enclosed in achamber. Ionizing radiation incident on the air or gas produces chargecarriers that recombine with and thereby change the charge on the gate.The change in gate charge is detected and provides a measure of theincident radiation dosage. While an effective dosimeter, the DISdosimeter has not been widely used because of the laborious (typicallymanual) and expensive fabrication process starting with a MOSFETtransistor, altering the transistor to expose the gate, and hermeticallysealing the modified transistor in a chamber.

There are many applications for dosimeters, from safety monitoring toindustrial process monitoring to medical imaging and radiotherapy. Amajor application is personal dosimetry for people who may be exposed toradiation; these include medical workers and patients. At present,dosimeters are usually exchanged on a periodic basis with newdosimeters, and the old dosimeters are sent to a service provider whoreads the dosimeters and provides data back to the user. Thus there is alot of handling and transportation of the dosimeters.

One particular application of great interest today is the detection ofpotential terrorist threats using nuclear materials. Since there aremany threat points, including airports, sea ports, border crossings,subways, large public buildings, shopping malls, and sports arenas, andmany ways of transporting contraband nuclear material, includingvehicles, shipping containers, luggage, and people, an effective systemrequires many dosimeters and real time data recovery. The military couldalso use dosimeters to locate nuclear materials and to monitor exposureof troops in the field.

To be widely used, a dosimeter should be low cost and easy tomanufacture. Furthermore, to be effective, it must be easy to obtaindata from the dosimeters in real time and to communicate thisinformation to a collection point. In some cases the dosimeters may bewidely distributed from the collection point; in other cases thedosimeters may all arrive at a common location. It would be particularlyuseful if the data could be collected using state of the arttelecommunications technology, e.g. the Internet.

Therefore, it is desirable to provide a DIS dosimeter design that is lowcost and easy to manufacture.

It is also desirable to provide a DIS dosimeter that has easy datareadout capability, including a DIS dosimeter with Internetconnectability or other telecommunication interfaces.

It is further desirable to provide a system that can read a plurality ofdosimeters in different locations or at a common location.

BRIEF SUMMARY

An aspect of the invention is a direct ion storage (DIS) radiationdosimeter, including a first layer having a MOSFET structure formedthereon by semiconductor processing techniques, the MOSFET structurehaving a floating gate with an exposed surface; a second layer having aconcavity therein; and a third layer, optionally having a concavitytherein; the first layer being sandwiched between the second and thirdlayer, the three layers being bonded together to form a hermetic seal;wherein the concavity in the second layer, and any concavity in thethird layer, are aligned with the exposed surface of the floating gateto form an ion chamber.

Another aspect of the invention is a direct ion storage (DIS) radiationdosimeter, including a MOSFET having a floating gate with an exposedsurface; a data conversion interface electrically connected to theMOSFET; and a communications interface connected to the output of thedata conversion interface; the data conversion and communicationsinterfaces being integral to the dosimeter.

Also an aspect of the invention is a system for screening a plurality ofpersons, objects, or containers at a location for radiation exposure orfor radioactive sources carried therein or thereon, including aplurality of dosimeters, a dosimeter being attached to each person,object, or container present at the location, each dosimeter having anintegral communications interface; and a dosimeter reader at thelocation for reading each dosimeter through its communications interfaceon a one time or on a periodic basis. The reader is connected to acentral station by wired or wireless communication.

A further aspect of the invention is a system for screening a pluralityof objects, containers or persons being transported from a firstlocation to a second location for radioactive sources carried therein orthereon, including a plurality of dosimeters, a dosimeter being attachedto each object, container, or person present at the first location, eachdosimeter having an integral communications interface; a first dosimeterreader at the first location for reading each dosimeter through itscommunications interface before the associated object, container, orperson leaves the first location; and a second dosimeter reader at thesecond location for reading each dosimeter through its communicationsinterface when the associated object, container, or person arrives atthe second location.

Yet another aspect of the invention is a system for surveillance of anarea for radioactive sources located therein, including a plurality ofdosimeters, each dosimeter being attached to a person or a vehicle thatmoves through the surveillance area, each dosimeter having an integralwireless communications interface and a locator device; and a reader incommunication with the dosimeters. The reader may be at a centralstation or communicate with a central station.

Yet a further aspect of the invention is a method for screening aplurality of persons, objects, or containers at a location for radiationexposure or for radioactive sources carried therein or thereon, byattaching a dosimeter to each person, object, or container present atthe location, each dosimeter having an integral communicationsinterface; and reading each dosimeter at the location through itscommunications interface on a one time or a periodic basis. Data readfrom each dosimeter at the location is transmitted to a central stationfor processing, and reports are received back from the central station,all electronically.

Another aspect of the invention is a method for screening a plurality ofobjects, containers or persons being transported from a first locationto a second location for radioactive sources carried therein or thereon,by attaching a dosimeter to each object, container, or person present atthe first location, each dosimeter having an integral communicationsinterface; reading each dosimeter through its communications interfacebefore the associated object, container, or person leaves the firstlocation; and reading each dosimeter through its communicationsinterface when the associated object, container, or person arrives atthe second location.

Also an aspect of the invention is a method for surveillance of an areafor radioactive sources located therein, by attaching a plurality ofdosimeters to persons or vehicles that move through the surveillancearea, each dosimeter having an integral wireless communicationsinterface and a locator device; and monitoring the plurality of mobiledosimeters at a reader in communication with the dosimeters. The readermay be at a central station or data from a reader can be sent to acentral station.

Further aspects of the invention will be brought out in the followingportions of the specification, wherein the detailed description is forthe purpose of fully disclosing preferred embodiments of the inventionwithout placing limitations thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood by reference to thefollowing drawings which are for illustrative purposes only:

FIGS. 1A, B are cross-sectional views of a basic prior art DIS radiationdetector, without and with a surrounding conductive wall.

FIGS. 2A, B are a cross-sectional view and an assembly drawing of athree layer dual chamber DIS dosimeter of the invention.

FIG. 3 is a block diagram of the components of a DIS dosimeter of theinvention having an internal readout.

FIGS. 4A-C are a perspective, an assembly, and a partly assembled andpartly in section drawing of a DIS dosimeter package of the invention.

FIGS. 4D-E are top views showing the operation of the pivotable baseelement of the DIS dosimeter package of FIGS. 4A-C.

FIGS. 5-6 are block diagrams of radiation detection systems of theinvention based on a plurality of dosimeters.

DETAILED DESCRIPTION OF THE INVENTION

Referring more specifically to the drawings, for illustrative purposesthe present invention is embodied in the apparatus, systems, and methodsgenerally shown in FIG. 1A through FIG. 6. It will be appreciated thatthe apparatus and systems may vary as to configuration and as to detailsof the parts, and the methods may vary as to the particularimplementation, without departing from the basic concepts as disclosedherein.

One aspect of the invention is directed to an improved direct ionstorage (DIS) dosimeter, and methods of making same. The basicconfiguration of the DIS dosimeter is shown in U.S. Pat. No. 5,739,541,which is herein incorporated by reference. As shown in FIG. 1A, DISdetector 10 is a modified MOSFET transistor and has a source 11 and adrain 12 separated by a channel 17 formed on a substrate 18. The DISdetector 10 also has an oxide layer 14 on the substrate 18 coveringchannel 17 and at least a portion of source 11 and drain 12. A floatinggate 15 is provided in the oxide layer 14, spaced above channel 17 andextending between source 11 and drain 12. Oxide layer 14 has an opening16 therein over the floating gate 15 so that at least a portion of thesurface of the floating gate 15 is uncovered and electricallynon-insulated. Opening 16 forms an air or gas space in direct contactwith floating gate 15.

In operation, a charge is placed on floating gate 15, e.g. by applying avoltage between source 11 and drain 12. When ionizing radiation isincident on the air or other gas above the (charged) floating gate 15,charge carriers will be produced and these will cause a change in thecharge on the gate 15 because of recombination. The change in charge onthe gate 15 is a measure of the radiation dosage. The change in chargeon the gate 15 can easily be measured, without disturbing the charge onthe gate 15, by measuring the conductivity of channel 17 between source11 and drain 12.

The basic DIS radiation detector 10 of FIG. 1A may be enclosed in aconducting wall 19 to produce DIS dosimeter 20 having a closed ionchamber 21 filled with air or other gas as shown in FIG. 1B. Dependingon the wall material and thickness, and the type of radiation, theincident radiation may interact with the wall and produce secondaryelectrons which then ionize the air or gas in the ion chamber 21, or theradiation may penetrate through the wall 19 and directly ionize the airor gas in chamber 21. In either case, the ionized air or gas in chamber21 will cause a change in the gate charge of the MOSFET that isproportional to the radiation dosage. Electrical leads 22, 23 to source11 and drain 12 extend out from dosimeter 20 so that charge may beapplied to the gate or gate charge changes (i.e. channel conductivitychanges) can be measured. If a particular type of radiation is beingdetected, materials that interact with that radiation should be used forthe wall. For example, for thermal neutron detection, boron or lithiumcontaining materials, e.g. plastic with boron nitride or polyethylenewith lithium nitrate, could be used, while for photon detection, thewalls could be made of teflon or graphite.

The invention includes a simplified three layer single or multiple ionchamber DIS radiation detector configuration, based on the abovedescribed principles, made by semiconductor packaging techniques, andmethods of making same. FIG. 2A shows an illustrative DIS radiationdetector 30 of the invention having two chambers, but the inventionincludes single chamber and more than two chamber detectors. Detector 30is made of three modular layers 32, 33, 34, which can each bemanufactured by automated processes. The three layers are then broughttogether and hermetically sealed together, again by automated processes,to form the detector 30, with two ion chambers 35, 36. The middle layer32 is the MOSFET layer; it is fabricated using standard semiconductorfabrication equipment and processes, typically on a silicon substrate.MOSFET layer 32 is formed by conventional steps of deposition, doping,and etching so that it has two MOSFET structures 31 with exposedfloating gates as described above and as illustrated in FIG. 1A. MOSFETlayer 32 also has conducting electrical lines 39 formed thereon so thatelectrical connection can be made to the source and drain of the MOSFETstructures 31 from outside the radiation detector 30.

Top and bottom layers 33, 34 are also made by automated processes,typically of metal or conducting polymer, in sizes and shapes to matchthe MOSFET layer 32. Top layer 33 includes concavities 37, 38 and bottomlayer 34 contains concavities 47, 48 so that when top and bottom layers33, 34 are brought together with and hermetically sealed to MOSFET layer32, ion chambers 35, 36 are formed. Concavity 37 in top layer 33communicates with concavity 47 in bottom layer 34 through MOSFET layer32 to increase the size of ion chamber 35; likewise for cavities 38, 48and ion chamber 36. Alternatively, the bottom layer 34 may besubstantially flat, and top cavities 37, 38 alone form the ion chambers35, 36. For assembly, the three layers 32, 33, 34 are aligned andbrought together, with MOSFET layer 32 sandwiched between top layer 33and bottom layer 34, as shown in FIG. 2B, and bonded together. Theelectrical lines 39 communicate externally through the detector 30 andare connected to standard electrical connectors (not shown) so thatcharge may be placed on the floating gate and changes in charge on thegate may be measured. In a simplified two layer embodiment, the bottomlayer 34 can be eliminated and the detector is formed by sealing the toplayer 34 to the MOSFET layer 32.

The two ion chambers 35, 36 may be of different sizes for differentradiation dosages. The pressures in the chambers may be selected fordesired sensitivity. Different gases may be used in the two chambers.Thus the dosimeters can be tailored to the application.

To best utilize the DIS radiation detector of FIGS. 1A, B, and inparticular the improved DIS radiation detector configuration of FIG. 2A,the invention further includes a radiation sensor package with anintegrated communications interface, as shown in FIG. 3. In theradiation detector package 40, the analog output of a DIS radiationdetector 42 passes through a data conversion (or signal conversion)interface 44, e.g. an analog-to-digital (A/D) converter, and thedigitized output of data conversion interface 44 is input to digitalcommunications interface 46. The data conversion and digitalcommunications interfaces 44, 46 may be combined in a data collectionand data readout integrated circuit 48. Interface 46 allows thedosimetry data to be communicated to many different systems. Interface46 can be selected from any of many available digital interfacetechnologies, particularly those for interfacing to the Internet. Oneparticular preferred interface is a USB port, allowing direct connectionor connection by USB cable to various readers. Any other wired interfacecan also be used. Another preferred interface is a wirelesstelecommunication interface, allowing wireless transmission of the datato various readers. The invention does not depend on a particularimplementation of the data conversion and communications interfaces, butmay be implemented with any presently available or future technologies.The implementation may include any and all features that are availablewith these technologies. For example, the implementation may includetamper proof algorithms, hardware or software to insure integrity of thesystem; features such as data integrity checking algorithms andencryption would normally be included.

The invention further includes a modular integrated DIS radiation sensoror dosimeter package, as shown in FIGS. 4A-E. The modular integrated DISradiation sensor package 50 is contained in a compact housing 51,typically made of plastic. Housing 51 has an aperture 52 in one endthereof. Sensor package 50 also includes a DIS radiation dosimeter orsensor 54 of the general type shown in FIGS. 1A, B, and more preferablythe configuration shown in FIG. 2A. The DIS radiation sensor 54 iselectrically connected to an associated data collection and data readoutintegrated circuit 56. DIS sensor 54 and integrated circuit 56 aremounted on a support frame 55 that fits into and is slidably mounted tohousing 51. Integrated circuit 56 includes a USB port or connection 57at one end thereof. Metal bracket 58 forms a shield to USB port orconnection 57 of integrated circuit 56. Bracket 59 is also part of theinternal sensor and circuit assembly 64. More generally, integratedcircuit 56 includes the data or signal conversion interface 44 anddigital communication interface 46 of FIG. 3. It provides for datacollection from sensor 54 and data readout from sensor package 50. In analternate embodiment, integrated circuit 56 may have a wirelesscommunication interface in place of the USB port. Sensor package 50 mayinclude, but does not require, an internal power source, e.g. a battery.Once the DIS sensor 54 has been charged from an external source, it willfunction as a dosimeter, i.e. the stored charge will change uponexposure to radiation. Integrated circuit 56 can be powered externally,e.g. inductively or RF interrogation, or by electrical connection, whenit is desired to read the data.

A base element 60 having a protective aperture closing flange 61extending therefrom is pivotably mounted to the bottom of housing 51 sothat flange 61 normally covers the aperture 52, as shown in FIG. 4A.Base element 60 has a mounting ring 65 that snaps into circular aperture66 on the bottom of housing 51. A rod 67 also extends upwardly from thering 65; rod 67 is distal from flange 61. Rod 67 engages a slot 53 onthe bottom of frame 55. Flange 61 is rotated away from aperture 52, asshown in FIGS. 4D-E, when it is desired to connect USB port 57 to anexternal reader. As base element 60 is rotated, camming action by rod 67slides the frame 55 forward toward the aperture 52. When flange 61 hasbeen rotated 180, frame 55 has been fully translated forwards so thatUSB connector 57 extends out from aperture 54, and may be plugged intothe USB port of a digital computer or other reader. Alternatively,closing flange 61 could be hinged at the bottom so that it could befolded down away from the aperture 52 and other mechanisms may be usedto slide the frame forward to extend the USB port 57. Base element 60also includes a clip 63 for easy attachment to a person or object. Otherattachment means could also be used. An optional radiation shield 68 mayalso be mounted in the housing 51, inside the top, over DIS sensor 54 toshield from certain radiation.

FIG. 5 illustrates a radiation detection system 70 of the invention. Aplurality (n) of objects, containers, or people 71 a, 71 b . . . 71 n ata first location 72 each have a radiation dosimeter 74 a, 74 b . . . 74n affixed thereto. The dosimeters 74 a . . . 74 n are preferably DISdosimeters as described above but may include other types of dosimeterssuch as TLD (thermoluminescent), OSL (optically stimulated luminescent),RPL (radiophosphorluminescent), radiochromic (RC) and MOSFET (old type,not DIS) dosimeters. In general, any type of passive dosimeter can beused. As a physical property changes when exposed to radiation, thechange can be measured. However, all the dosimeters have a built incommunications interface, e.g. as shown in FIG. 3. For example, any ofthese other types of dosimeters could replace DIS sensor 54 in sensorpackage 50 of FIG. 4A-E.

Also located at the first location 72 is a first reader 75 for readingthe data from each of the dosimeters 74 a . . . 74 n. Reader 75 may beany type of device that can collect the data from the dosimeters throughthe built in communications interfaces of the dosimeters. For example,reader 75 may be connected to a dosimeter by a USB cable 77, as shownwith dosimeter 74 a, or the reader 75 may be in wireless communicationwith a dosimeter, as shown with dosimeter 74 n. Reader 75 may also bedirectly connected to the dosimeter using an extendable USB connector asshown in FIG. 4E. Reader 75 may typically be a PC.

The individual dosimeters 74 a . . . 74 n do not have to have aninternal power source, e.g. batteries, which may be removed or otherwisebecome disabled. The individual dosimeters 74 a . . . 74 n may insteadbe inductively powered, e.g. by the reader 75. This will ensure that atthe time that it is desired to read a particular dosimeter to determineif the associated object, container, or person contains, is carrying, orhas been exposed to radioactive material, the dosimeter will be properlypowered.

Location 72 may be a single location where dosimeter monitoring occurson a continuous or periodic basis. For example, it may be a nuclearreactor or medical radiotherapy center where system 70 is used forpersonal dosimetry. The personnel 71 a . . . 71 n at the location 72 aresubject to periodic readings of the dosimeters 74 a, . . . 74 n thatthey wear while present. This is done by simply reading the dosimetersat scheduled intervals by the on site reader 75, e.g. by USB or wirelessconnection. Location 72 may also be a location where visitors arescreened upon leaving or a processing facility where products arescreened when being shipped. For example it may be a manufacturingfacility where shipping containers are screened prior to shipment byattaching a dosimeter and reading the dosimeter at the on site reader todetect any residual radiation or radioactive contaminants. Location 52could be in camp or field headquarters in a military theater, wheresoldiers plug in to a PC to monitor possible exposure or to locatehidden weapons. The PC can be in wireless or wired communication with acentral command post. Location 52 could also be an airport wherearriving flight crews could have their dosimeters read to monitorexposure to cosmic rays.

Location 72 may also be the point of origin, e.g. an airport, a seaport,a railroad station, or a factory, of objects, containers or people 74 a. . . 74 n that are to be transported to a second location. The set ofdosimeters 74 a . . . 74 n and the reader 75 allow an assessment ofwhether any radioactive material is present prior to transport to asecond location 78, the point of destination. Any objects, containers orpeople for which the dosimeters show the presence of radiation can beremoved or otherwise investigated. The remaining objects, containers orpeople, with their affixed dosimeters, can then be transported tolocation 78.

At location 78, a second reader 79 is present and the data on theaffixed dosimeters is again read. Reader 79 is similar to reader 78 andreads the data from the dosimeters through the built in communicationsinterface. This second reading at the destination location preventsradioactive material from being picked up or added after leaving thefirst location. Again, if any of the objects, containers or persons readpositive for radiation, they can be isolated and not passed on.

The readers 75, 79 at locations 72, 78 may also be in communication witha central station 80 at a third location 84. This communication may beover wires 81 or by wireless links 82. Central station 80 may collectall the data from a plurality of locations and coordinate security ormonitoring efforts. For example, in the case of personal monitoring on aperiodic basis at a single location, central station 80 collects thedata from the reader at that location and sends back dosimetry reports.Since the communications system can be implemented on the Internet, thereports can be sent on the internet, and viewed by personnel back at themonitored location. Thus, the physical transfer of dosimeters and paperreports is eliminated. In the case of transport of containers betweentwo locations, central station 80 can receive data from reader 75 atorigin location 72, process the data, and provide a report, on theInternet, that is available at destination location 78 by the time thecontainers arrive there. Reports back to any location can be very rapidsince data collection, processing and reporting are all doneelectronically.

The invention includes methods of detecting radiation exposure orradiation sources through a system of dosimeters as illustrated in FIG.5. One method involves screening at a single location, either singly oron a periodic basis. This method includes screening a plurality ofobjects, containers, or people at the location by reading out dosimetersaffixed to the objects, containers or people through communicationsinterfaces in the dosimeters. The dosimeters are read locally; the datamay then be transmitted to a remote central station for processing,report preparation etc. Another method tracks objects, containers orpeople from one location to another. The method includes first screeninga plurality of objects, containers, or people at a first location bylocally reading out dosimeters affixed to the objects, containers orpeople through communications interfaces in the dosimeters. Aftertransport to a second location, the same plurality of objects,containers or people are again screened by locally reading out theaffixed dosimeters through their communications interfaces. The readoutsfrom the first and second locations may also be transmitted to a centralstation. In both methods, readout of the dosimeters at the locations,and communications from the locations to the central station and backare all electronic and thus very rapid. The methods can be implementedon the Internet for easy access by users.

FIG. 6 illustrates a radiation detection system 90 of the invention. Aplurality (n) of people or vehicles 91 a, 91 b . . . 91 n each have aradiation dosimeter 92 a, 92 b . . . 92 n affixed thereto. Thedosimeters 92 a . . . 92 n are preferably DIS dosimeters as describedabove but may include other types of dosimeters such as TLD, MOSFET,RPL, RC and OSL dosimeters. However, all dosimeters have a built incommunications interface, e.g. as shown in FIG. 3. The communicationsinterface preferably is a wireless communications interface so that itmay send data from any location. Each person or vehicle 91 a . . . 91 nmoves through an associated area 93 a . . . 93 n. The areas 93 a . . .93 n may overlap, as 93 a and 93 b, or even be coincident, i.e. multiplepersons or vehicles could cover the same area, as 93 b and 93 c.

The individual dosimeters 92 a . . . 92 n all communicate with a centralstation 95, e.g. wirelessly. Central station 95 includes a reader forreading the data from each of the dosimeters 92 a . . . 92 n. The readermay be any type of device that can collect the data from the dosimetersthrough the built in communications interfaces of the dosimeters.Alternatively, there could be a number of readers 94 a, 94 b . . . 94 mplaced at nearby locations, i.e. either inside areas 93 a . . . 93 n, asreader 94 a or 94 b, or close to an area, as reader 94 m. The persons orvehicles could then wirelessly communicate with a nearby reader or go tothe reader and have the dosimeter read; the reader would then transmitthe data to the central station.

As the individual persons or vehicles move through the areas, theassociated dosimeters will monitor the surroundings. These dosimeterswill generally carry their own power source, e.g. batteries, or beconnected to the vehicle electrical system; alternatively they could beexternally powered, e.g. inductively or by RF interrogation. Anypositive signals from the dosimeters will be monitored by the centralstation, either directly or through localized readers. The dosimeterscan include a GPS or other tracking device so that its location canreadily be determined. Again, because data collection and transmissionare all electronic, identification of any problems can be almostinstantaneous.

The invention includes a method of detecting radiation sources using thesystem of dosimeters as shown in FIG. 6. A plurality of mobiledosimeters are provided, e.g. by being carried on or being affixed topeople, e.g. mailmen or meter readers, or vehicles, e.g. police cars,buses, taxis or delivery trucks. The mobile dosimeters include internalcommunications interfaces, preferably wireless. As the people orvehicles with the dosimeters move through an area, either on a fixedroute or at random, a central station monitors the dosimeters throughthe dosimeter communications interfaces. Alternatively the dosimetersmay be read by local readers, e.g. at the post office or policestations, and the local readers transmit the data to the centralstation. One particular application is for military personnel in thefield. While patrolling or even during battle, the dosimeters, either onthe soldiers or on their vehicles, can be in communication with a readerto provide essentially real time information about radiation exposure.

While the ability to easily read out data from the dosimeter byproviding an internal communications interface is an important aspect ofthe invention, an optional feature is have two way communication. If thereader is a PC, then the user can get feedback, i.e. reports, on the PCdisplay. However, in some cases, particularly in the field, it may bedesirable to add an alarm receiver circuit to the dosimeter so that thecentral station can send an alarm signal to the individual dosimeter.This signal could then actuate a visual Indicator, e.g. light, colorbar, or numeric value display, sound, vibration or other indicator toalert the user. The digital communications interface 46 of FIG. 3 couldinclude an alarm signal receiver 47 connected to an indicator device 49.

While the dosimeters of the invention can be used alone, or as parts ofthe multi-dosimeter systems, they may also be incorporated assubcomponent parts of other devices. For example, the dosimeters couldbe part of a cell phone, radio, smoke detector, electronic dosimeter,surveillance camera and other communications or monitoring devices.

While the DIS dosimeter of the invention has been implemented with aMOSFET with exposed floating gate, other nonvolatile charge storageelements could be used if they become available.

The invention thus provides an improved DIS radiation detector ordosimeter that is easy and low cost to manufacture using well knownsemiconductor processing techniques. The detectors include internalcommunications interfaces so they are easy to read. Differentinterfaces, including USB ports and wireless interfaces, may be used, sothat the dosimeters may be read over the internet. The detectors canthus be deployed or used in a variety of detection systems and screeningmethods.

Although the description above contains many details, these should notbe construed as limiting the scope of the invention but as merelyproviding illustrations of some of the presently preferred embodimentsof this invention. Therefore, it will be appreciated that the scope ofthe present invention fully encompasses other embodiments which maybecome obvious to those skilled in the art, and that the scope of thepresent invention is accordingly to be limited by nothing other than theappended claims, in which reference to an element in the singular is notintended to mean “one and only one” unless explicitly so stated, butrather “one or more.” All structural and functional equivalents to theelements of the above-described preferred embodiment that are known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the present claims.Moreover, it is not necessary for a device to address each and everyproblem sought to be solved by the present invention, for it to beencompassed by the present claims. Furthermore, no element or componentin the present disclosure is intended to be dedicated to the publicregardless of whether the element or component is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112, sixth paragraph, unless the element isexpressly recited using the phrase “means for.”

Concepts

As short summaries, this writing has disclosed at least the followingbroad concepts.

Concept 1. A direct ion storage (DIS) radiation dosimeter, comprising:

-   -   a first layer having a MOSFET structure formed thereon by        semiconductor processing techniques, the MOSFET structure having        a floating gate with an exposed surface;    -   a second layer having a concavity therein;    -   a third layer, optionally having a concavity therein;    -   the first layer being sandwiched between the second and third        layer, the three layers being bonded together to form a hermetic        seal;    -   wherein the concavity in the second layer, and any concavity in        the third layer, are aligned with the exposed surface of the        floating gate to form an ion chamber.

Concept 2. The dosimeter of Concept 1 wherein the first layer has morethan one MOSFET structure formed thereon, and the second layer has acorresponding number of concavities, and the third layer optionally hasa corresponding number of concavities, to form an ion chamber over eachMOSFET structure.

Concept 3. The dosimeter of Concept 2 wherein each ion chamber has adifferent size.

Concept 4. The dosimeter of Concept 2 wherein each ion chamber is filledwith a different gas.

Concept 5. The dosimeter of Concept 2 wherein each ion chamber is filledwith a gas at a different pressure.

Concept 6. A direct ion storage (DIS) radiation dosimeter, comprising:

-   -   a MOSFET having a floating gate with an exposed surface;    -   a data conversion interface electrically connected to the        MOSFET;    -   a communications interface connected to the output of the data        conversion interface;    -   the data conversion and communications interfaces being integral        to the dosimeter.

Concept 7. The dosimeter of Concept 6 wherein the communicationsinterface is a wired interface.

Concept 8. The dosimeter of Concept 7 wherein the communicationsinterface is a USB port or connection.

Concept 9. The dosimeter of Concept 6 wherein the communicationsinterface is a wireless interface.

Concept 10. The dosimeter of Concept 6 wherein the communicationsinterface includes data integrity checking and encryption.

Concept 11. The dosimeter of Concept 6 wherein the dosimeter isconnected to the internet through the communications interface.

Concept 12. The dosimeter of Concept 6 wherein the data conversion andcommunications interfaces are externally powered.

Concept 13. The dosimeter of Concept 12 wherein the data conversion andcommunications interfaces are powered inductively or by RFinterrogation, or by electrical connection to an external power source.

Concept 14. The dosimeter of Concept 6 wherein the communicationsinterface further comprises an alarm signal receiving circuit.

Concept 15. The dosimeter of Concept 14 further comprising an indicatordevice connected to the alarm signal receiving circuit.

Concept 16. A system for screening a plurality of persons, objects, orcontainers at a location for radiation exposure or for radioactivesources carried therein or thereon, comprising:

-   -   a plurality of dosimeters, a dosimeter being attached to each        person, object, or container present at the location, each        dosimeter having an integral communications interface;    -   a dosimeter reader at the location for reading each dosimeter        through its communications interface on a one time or on a        periodic basis.

Concept 17. The system of Concept 16 wherein the communicationsinterface in each dosimeter is a wired or a wireless communicationsinterface.

Concept 18. The system of Concept 17 wherein the interface is a USBinterface.

Concept 19. The system of Concept 16 wherein the dosimeters are DIS,TLD, OSL, RPL, RC, MOSFET or other passive dosimeters.

Concept 20. The system of Concept 16 further comprising a centralstation to which the reader is connected by wired or wirelesscommunication.

Concept 21. A system for screening a plurality of objects, containers orpersons being transported from a first location to a second location forradioactive sources carried therein or thereon, comprising:

-   -   a plurality of dosimeters, a dosimeter being attached to each        object, container, or person present at the first location, each        dosimeter having an integral communications interface;    -   a first dosimeter reader at the first location for reading each        dosimeter through its communications interface before the        associated object, container, or person leaves the first        location;    -   a second dosimeter reader at the second location for reading        each dosimeter through its communications interface when the        associated object, container, or person arrives at the second        location.

Concept 22. The system of Concept 21 wherein the communicationsinterface in each dosimeter is a wired or a wireless communicationsinterface.

Concept 23. The system of Concept 22 wherein the interface is a USBinterface.

Concept 24. The system of Concept 21 wherein the dosimeters are DIS,TLD, OSL, RPL RC, MOSFET or other passive dosimeters.

Concept 25. The system of Concept 21 further comprising a centralstation to which the first and second readers are connected by wired orwireless communication.

Concept 26. A system for surveillance of an area for radioactive sourceslocated therein, comprising:

-   -   a plurality of dosimeters, each dosimeter being attached to a        person or a vehicle that moves through the surveillance area,        each dosimeter having an integral communications interface;    -   a reader in communication with the dosimeters.

Concept 27. The system of Concept 26 wherein the communicationsinterface in each dosimeter is a wired or a wireless communicationsinterface.

Concept 28. The system of Concept 27 wherein the interface is a USBinterface.

Concept 29. The system of Concept 26 wherein the dosimeters are DIS,TLD, OSL, RPL, RC, MOSFET or other passive dosimeters.

Concept 30. The system of Concept 26 wherein each dosimeter furthercomprises a locator device.

Concept 31. A method for screening a plurality of persons, objects, orcontainers at a location for radiation exposure or for radioactivesources carried therein or thereon, comprising:

-   -   attaching a dosimeter to each person, object, or container        present at the location, each dosimeter having an integral        communications interface;    -   reading each dosimeter at the location through its        communications interface on a one time or a periodic basis.

Concept 32. The method of Concept 31 wherein the communicationsinterface in each dosimeter is a wired or a wireless communicationsinterface.

Concept 33. The method of Concept 32 wherein the interface is a USBinterface.

Concept 34. The method of Concept 31 wherein the dosimeters are DIS,TLD, OSL, RPL, RC, MOSFET or other passive dosimeters.

Concept 35. The method of Concept 31 further comprising transmittingdata read from each dosimeter at the location to a central station forprocessing, and receiving reports back from the central station.

Concept 36. The method of Concept 35 wherein transmitting data to thecentral station and receiving reports back are performed over theInternet.

Concept 37. A method for screening a plurality of objects, containers orpersons being transported from a first location to a second location forradioactive sources carried therein or thereon, comprising:

-   -   attaching a dosimeter to each object, container, or person        present at the first location, each dosimeter having an integral        communications interface;    -   reading each dosimeter through its communications interface        before the associated object, container, or person leaves the        first location;    -   reading each dosimeter through its communications interface when        the associated object, container, or person arrives at the        second location.

Concept 38. The method of Concept 37 wherein the communicationsinterface in each dosimeter is a wired or a wireless communicationsinterface.

Concept 39. The method of Concept 38 wherein the interface is a USBinterface.

Concept 40. The method of Concept 37 wherein the dosimeters are DIS,TLD, OSL, RPL, RC, MOSFET or other passive dosimeters.

Concept 41. The method of Concept 37 further comprising transmittingdata read from the dosimeters at the first and second locations to acentral station.

Concept 42. A method for surveillance of an area for radioactive sourceslocated therein, comprising:

-   -   attaching a plurality of dosimeters to persons or vehicles that        move through the surveillance area, each dosimeter having an        integral communications interface;    -   monitoring the plurality of mobile dosimeters at a reader in        communication with the dosimeters.

Concept 43. The method of Concept 42 wherein the communicationsinterface in each dosimeter is a wired or a wireless communicationsinterface.

Concept 44. The method of Concept 43 wherein the interface is a USBinterface.

Concept 45. The method of Concept 42 wherein the dosimeters are DIS,TLD, OSL, RPL, RC, MOSFET or other passive dosimeters.

Concept 46. The method of Concept 42 wherein each dosimeter furthercomprises a locator device.

Concept 47. The method of Concept 42 wherein the reader is located at acentral station.

Concept 48. The method of Concept 42 further comprising transmittingdata from the reader to a central station.

Concept 49. A direct ion storage (DIS) radiation dosimeter package,comprising:

-   -   a housing having an aperture in an end thereof;    -   a frame fitting inside and slidably mounted in the housing;    -   a DIS radiation sensor mounted on the frame;    -   a data collection and data readout integrated circuit        electrically connected to the DIS radiation sensor and mounted        on the frame;    -   the data collection and data readout integrated circuit having a        USB connection at one end thereof proximal to the aperture;    -   a base element rotatably attached to housing so that as the base        element is rotated, the frame slides toward the aperture and the        USB connection extends outside the aperture.

1. A direct ion storage (DIS) radiation dosimeter, comprising: a firstlayer having a MOSFET structure formed thereon by semiconductorprocessing techniques, the MOSFET structure having a floating gate withan exposed surface; a second layer having a concavity therein; a thirdlayer, optionally having a concavity therein; the first layer beingsandwiched between the second and third layer, the three layers beingbonded together to form a hermetic seal; wherein the concavity in thesecond layer, and any concavity in the third layer, are aligned with theexposed surface of the floating gate to form an ion chamber.
 2. Thedosimeter of claim 1 wherein the first layer has more than one MOSFETstructure formed thereon, and the second layer has a correspondingnumber of concavities, and the third layer optionally has acorresponding number of concavities, to form an ion chamber over eachMOSFET structure.
 3. The dosimeter of claim 2 wherein each ion chamberhas a different size.
 4. The dosimeter of claim 2 wherein each ionchamber is filled with a different gas.
 5. The dosimeter of claim 2wherein each ion chamber is filled with a gas at a different pressure.6. (canceled)
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 49. A direct ion storage (DIS) radiationdosimeter package, comprising: a housing having an aperture in an endthereof; a frame fitting inside and slidably mounted in the housing; aDIS radiation sensor mounted on the frame; a data collection and datareadout integrated circuit electrically connected to the DIS radiationsensor and mounted on the frame; the data collection and data readoutintegrated circuit having a USB connection at one end thereof proximalto the aperture; a base element rotatably attached to housing so that asthe base element is rotated, the frame slides toward the aperture andthe USB connection extends outside the aperture.
 50. The dosimeter ofclaim 1 wherein the third layer has a concavity and the concavity in thesecond layer communicates with the concavity in the third layer throughthe first layer.
 51. The dosimeter of claim 1 further comprising: a dataconversion interface electrically connected to the MOSFET structure; acommunications interface connected to the output of the data conversioninterface; the data conversion and communications interfaces beingintegral to the dosimeter.
 52. The dosimeter of claim 51 wherein thecommunications interface is a wired interface.
 53. The dosimeter ofclaim 52 wherein the communications interface is a USB port orconnection.
 54. The dosimeter of claim 51 wherein the communicationsinterface is a wireless interface.
 55. The dosimeter of claim 51 whereinthe communications interface includes data integrity checking andencryption
 56. The dosimeter of claim 51 wherein the dosimeter isconnected to the internet through the communications interface.
 57. Thedosimeter of claim 51 wherein the data conversion and communicationsinterfaces are externally powered.
 58. The dosimeter of claim 57 whereinthe data conversion and communications interfaces are poweredinductively or by RF interrogation, or by electrical connection to anexternal power source.
 59. The dosimeter of claim 51 wherein thecommunications interface further comprises an alarm signal receivingcircuit.
 60. The dosimeter of claim 59 further comprising an indicatordevice connected to the alarm signal receiving circuit.
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 72. The DIS radiation dosimeter package of claim 49wherein the DIS radiation sensor comprises: a first layer having aMOSFET structure formed thereon by semiconductor processing techniques,the MOSFET structure having a floating gate with an exposed surface; asecond layer having a concavity therein; a third layer, optionallyhaving a concavity therein; the first layer being sandwiched between thesecond and third layer, the three layers being bonded together to form ahermetic seal; wherein the concavity in the second layer, and anyconcavity in the third layer, are aligned with the exposed surface ofthe floating gate to form an ion chamber.
 73. The DIS radiationdosimeter package of claim 49 wherein the data collection and datareadout integrated circuit includes data integrity checking andencryption.
 74. The DIS radiation dosimeter package of claim 49 whereinthe data collection and data readout integrated circuit is externallypowered.
 75. The DIS radiation dosimeter package of claim 74 wherein thedata collection and data readout integrated circuit is poweredinductively or by RF interrogation, or by electrical connection to anexternal power source.
 76. The DIS radiation dosimeter package of claim49 wherein the data collection and data readout integrated circuitfurther comprises an alarm signal receiving circuit.
 77. The DISradiation dosimeter package of claim 76 further comprising an indicatordevice connected to the alarm signal receiving circuit.
 78. The DISradiation dosimeter package of claim 72 wherein the third layer has aconcavity and the concavity in the second layer communicates with theconcavity in the third layer through the first layer.